This invention relates to improved portable abrading tools in which particles abraded from a work surface are withdrawn by suction through the tool to a collection location.
The tools of the present invention are of a known general type in which a portable body adapted to be held by a user contains a motor acting to drive a work contacting abrading structure rotatively about an axis. The abrading structure includes a rotary backing unit adapted to carry a sheet of sandpaper or other abrading material at the forward side of that unit and containing one or more passages through which a flow of air and entrained abraded particles are drawn by suction to the rear side of the backing unit. A shroud is provided at the rear side of the backing unit to define a chamber through which the air and entrained particles flow in confined relation to an outlet leading to the accumulation point.
In prior devices of this type having such rotary backing units and non-rotating shrouds co-acting therewith, there has been a tendency for the rapid rotary motion of the backing unit to cause abraded particles contacting that unit to move radially outwardly at the rear side of the backing unit under the influence of centrifugal force, with some resultant tendency for these centrifugally urged particles to then escape past the periphery of the backing unit and between it and the stationary shroud to the exterior of the shroud. The rate of flow of suction air through the device may under some circumstances be insufficient to overcome this centrifugal effect and prevent unwanted escape of the abraded particles into the atmosphere.